Comments on OET Lab Policy Document

There have been 4 comment(s) made on this document:

Mike Ramnath commented on 2012-07-27 09:46:54.02:

Additional comments on KDB 643646 Section IV starting on page 13

A.2 - we suggest removing "mitigate exposure concerns for" in the last sentence, to read, "apply general population exposure requirements to passengers and bystanders."

A.3. (i) does not represent (and should not be) a requirement, so it can be moved to the beginning of A.3. (ii) and the paragraphs renumbered accordingly.
A.4. (ii).(a) - this additional step should be removed, or alternatively required only for the highest MPE configuration found. Otherwise, the number of MPE measurements would increase multi-fold. MPE is a very conservative exposure metric compared with SAR. Such a multi-fold increase would negate the operational efficiencies that device manufacturers are able to achieve by using such a conservative approach.
A.4. (ii).(a) - the requirement to evaluate MPE along 0, 45, 90 degree radials seem to contradict similar requirements in the proposed revision of KDB 447498 [7.A.6.(ii)], where a 30-degree radial step is required. For vehicular mount antennas addressed in 643646, this additional step should be preferably removed, or alternatively required only for the highest MPE configuration found.
A.4. (ii).(a) - the current verbiage indicates that the 90 degree radial measurements are to be conducted "if applicable". The same "if applicable" condition should apply to the 45 degree measurements.
C.2.(ii) - in the comments previously submitted, we already highlighted the fact that the proposed 20-25% agreement required between simulated and measured power density, particularly in the point-by-point comparisons, would be very difficult to achieve given the intentional conservative bias employed in simulations. We want to reinforce this point by showing that it would be extremely unlikely to achieve a 25% agreement, point by point, even if simulations reproduced exactly the distribution of E^2 and H^2. For instance, assuming MPE point-measurements with 20% Gaussian uncertainty and statistical independence between point-measurements, the probability to be within 25% at all 10 measurement points [erf(0.25/0.2/sqrt(2))^10] would be only 9.3%; for 20 points it would be 0.9%.
KDB 643646 makes reference to KDB 447498 for MPE measurement guidance. The latter, at 7.A.6.(iii), provides guidance that may lead to subjective interpretations regarding the "exposed portions of a person's body". We suggest that KDB 643646 provide a superseding definition of the bystander MPE test method stating that a 2 meter vertical line be used for MPE averaging, as currently done when testing bystander exposure for vehicular mobile radios. Furthermore, KDB 447498
7.A.6.(iii).(a) states the requirement to have 10 cm steps for MPE tests which would lead to a two-fold increase of measurements compared to current practices for vehicular mobile radios, which allow 20 cm step. Given the fact that for frequencies below 1 GHz there is ample evidence (for instance simulations showing compliant SAR even when MPE measured at 20 cm increments - is above the limit) that the current method provides a reliable compliance framework, we suggest to define in KDB 643646 the MPE measurement step of 20 cm up to 1 GHz and reduce it in proportion to the wavelength above 1 GHz, so for instance it would be 10 cm at 2 GHz, 5 cm at 4 GHz, and so on. The test methods so defined in KDB 643646 would supersede those in KDB 447498.

Peter Jakubiec commented on 2012-07-03 21:46:54.02:
Relying on conducted power to determine the highest channel in low frequency PTT radios may not be the best method (the output power variation often is less than 0.5 dB), my idea is to use pre-scanning and area scan (based on Motorola Fast SAR) for each antenna, and channel combination to find the worst case channel, this is important as antenna gain varies significantly across the frequency range especially in the presence of the test liquid and measurements are done in near field, which makes it nearly impossible to tell which is the highest channel based on conducted power and not on pre-scanning. At these frequencies antennas are usually cut (tuned) for small frequency ranges (sub-bands). As you can see from the attached example (tests that were conducted last year) the highest conducted power gave the lowest SAR (few times lower than highest SAR) and also coincidentally the highest SAR was for the same antenna at the other end of frequency range for that antenna. Clearly this cannot be overlooked and ignored, we found that pre-scanning is quite accurate and the difference between Motorola Fast SAR and "zoom scan" is only in order of few %. The attached table shows clearly that if SAR was proportionally higher across the channels (i.e. less spacing) the criteria by which channels to test are chosen would cause that the worst case would have been missed and potentially exciding SAR limits significantly. Perhaps Fast Motorola SAR should be part of number of channel reduction method - in my opinion it would be more accurate and better in eliminating unnecessary testing. View attachment associated with this comment

Chuck Powers commented on 2012-06-29 16:43:05.42:
The United States has often supported the development of scientifically-based international standards in important regulatory areas. There are significant benefits from using harmonized rules and guidelines that are based on international exposure and assessment standards to ensure consistent testing methodologies for verifying compliance of wireless equipment with the applicable RF energy exposure limits for occupational users and for the general population. Because of the substantial safety margins built into these science-based exposure limits, compliance with these standards provides a sound scientific basis for confidence in the safety of products using RF energy. Reviews of independent expert groups and health authorities around the world over the last twelve years have consistently concluded that there are no proven adverse effects at these internationally accepted exposure limits. Motorola Solutions strongly supports harmonized standards for the assessment of RF emitting products under these exposure standards, to avoid the confusion and cost of having to test global products under multiple different test regimes. Given the substantial safety margins in these exposure standards, regulators can be confident that using scientifically-based international assessment standards is adequate to ensure that products are within the exposure limits. Any new assessment techniques should be introduced first into the appropriate international standards group for global discussion, acceptance and harmonization. Attaching new, unique US requirements to the already complicated compliance testing protocols adds to the complexity and multiplicity of different test regimes that manufacturers must operate under, without providing added benefit, yet causing increased efforts and cost. 1. KDB 643646 [Page 13, item IV.A.4 (i)]: The ability of Public Safety personnel to continue to use reliable Mobile PTT two-way radios installed in vehicles is a primary concern because of the newly proposed compliance evaluation distances for testing (≤90 cm from the antenna, ≥20 cm from vehicle, and 10 cm from back seat). To be compliant at these distances, Public Safety customers may no longer be able to buy 75-100 Watt (or higher) 2-way mobile radios and may need to purchase additional or new infrastructure to retain the present communications range provided by 75-100 Watt mobiles. The corresponding loss in territorial coverage would cause problems for Public Safety communication particularly in rural areas where high power mobile radios enable reliable communications. Under item IV.A.4 (ii) of this KDB, the bystander exposure would be evaluated at a 90 cm maximum distance from the vehicle if the antenna is mounted on the edge of the vehicle. We agree that the bystander separation distance from the vehicle should be at least 20 cm or 8 inches and no more than 90 cm or 3 ft. (about a small vehicle door width), consistent with the proposed KDB guidance. However, we propose that the evaluation distance between the bystander and the antenna should not be restricted to 90 cm, which will unnecessarily limit the power of the radios. We believe that the current approach used by Motorola Solutions, which tells the user specifically what a compliant distance is for a certain radio, is by far the most workable approach and has proven to be effective over many years. If the OET feels still that some maximum distance to the antenna should be imposed on this approach, we propose instead using up to 150 cm or 5 ft. distance to the antenna, which would allow for the addition of some of the distance between the antenna and the edge of the vehicle to supplement the 90 cm distance from the vehicle. In addition we propose that the guideline for backseat passenger testing should remain at 20 cm from the backseat to be consistent with IEEE C95.3-2002 standard and to avoid potential interaction of the measuring probe with any metallic content of the backseat. 2. KDB 643646 [Page 14, item IV.C.2]: The SAR simulation validation requirements set forth in the proposed KDB 643646 revision are unduly restrictive because they do not allow for a conservative bias in the simulated power density levels versus measurements. Where a product meets the FCC requirements even when the method used to assess the product overstates the exposure level, and the manufacturer uses that assessment method because it reduces test time and complexity, this is an efficient and safe approach for product assessment, and there is no reason now to exclude that approach. The FCC has consistently accepted and even promoted a conservative bias in exposure assessments and we urge the OET not to adopt this KDB revision as it is proposed, which might preclude the appropriate use of product assessment approaches that incorporate an intentional conservative bias. For instance, the referenced IEEE/IEC 62704-2 draft standard defines the simulation models with intentional conservative bias (reduced cable loss, no antenna mismatch loss, no ohmic loss in the car model, etc.) which in general will yield higher simulated field strength around the car compared to the measured field. This in turn will make it very difficult to achieve the proposed 20-25% agreement between simulated and measured power density, particularly in the point-by-point comparisons, also considering that the car used in the measurements may differ from the one specified in the referenced IEEE/IEC 62704-2 draft standard. Such conservative approaches are in addition to the substantial conservative safety factors already built into the FCC exposure limits. We propose that the additional validation steps defined in IV.C.2 be triggered when the source-based time-averaged maximum conducted output power is >70 W (before applying the 50% PTT duty cycle) or when the 1-g SAR (computed before the additional conservative scaling factor, if required, is applied to account for variation in population per IEEE/IEC 62704-2 draft standard) is >1.2 W/kg for general public exposure, and >6 W/kg for occupational exposure. In addition, said validation should be deemed acceptable if the average computed power density is 80% or higher than, and the peak power density is 75% or higher than, the corresponding measured values. It should also be clarified that the conservative SAR scaling factors in the referenced IEEE/IEC 62704-2 draft standard have been defined for and therefore apply only to bystander exposure to trunk-mount antennas, while any applicable factors for other exposure conditions are under investigation by the IEEE/IEC committee. 3. KDB 643646 [page 14, item IV.A.6]: The word Caution has specific recognized meaning under international norms and this meaning is not consistent with the proposed application here. The word Attention would be more appropriate. This would be consistent with the approved product label containing the RF Exposure icon and the word Attention that is set forth in the TIA TSB 133 Section 3.1. That label was created in collaboration with the FCC, and is a sound precedent for use of the word Attention instead of Caution. We are also recommending that manufacturers be given the flexibility of using a screen flash instead of a hard label, provided that the screen flash contains the same information that would appear on the hard label.

Brian Scarpelli commented on 2012-06-29 16:36:34.486:
The Telecommunications Industry Association (TIA) hereby submits input to the Federal Communications Commissions (FCC) Office of Engineering and Technology (OET) on draft Laboratory Division Knowledge Database (KDB) publication 643646 (What are the Specific Absorption Rate [SAR] test requirements for occupational push-to-talk [PTT] radios?) (KDB 643646). Specifically, TIA submits the following input for OETs consideration: In item 4(i) (page 13), the ability of Public Safety officers to continue to use important Mobile PTT 2-way radios installed in vehicles is a primary concern because of the newly proposed compliance evaluation distances for testing (90 cm from the antenna, 20 cm from vehicle, and 10 cm from back seat). To be in compliance at these distances, Public Safety customers may no longer be able to buy 75-100 Watt (or higher) 2-way mobile radios and may need to purchase additional or new infrastructure to retain their present communications range provided by 75-100 Watt mobiles. This could cause problems for safety communication in rural areas where high power radios are needed. Based on item 4(ii), the bystander exposure should be evaluated at a 90 cm maximum distance from the vehicle if the antenna is mounted on the edge of the vehicle. We propose that the bystander separation distance from the vehicle should be at least 20 cm or 8 inches and no more than 90 cm or 3 ft. (about a small vehicle door width), which is consistent with the drafted KDB guidance. But we propose that the evaluation distance between the bystander and the antenna should not be restricted to 90 cm, which will limit the power of radios. In addition we propose that the guideline for backseat passenger testing should remain at 20 cm from the backseat to be consistent with IEEE C95.3-2002 standard and to avoid potential interaction of the measuring probe with any metallic content in the backseat. The SAR simulation validation requirements set forth in the proposed KDB 643646 revision is unduly restrictive because they do not allow for a conservative bias in the simulated power density levels versus measurements. Where a product meets the FCC requirements even when the method used to evaluate the product overstates the exposure level, and the manufacturer uses that test method because it reduces test time and complexity, this is an efficient and safe approach for product evaluation. The FCC has consistently accepted and even promoted a conservative bias in exposure assessments and we propose that you continue to do so. Our interpretation of the requirements described in Sections III(A) and III(B) is that following this guidance obviates the need for submission of KBD inquiries. Please advise if such an interpretation is correct. Section IV wording implies that testing/evaluation of mobile PTT radios operating with vehicle-mounted antennas must now be accomplished using actual vehicle installations. Is this correct? If correct, what is a large vehicle, and what is a small vehicle? Do the definitions vary according to actual antenna placement, i.e. roof mount vs. trunk mount, etc.? Section IV(3iii) states The minimum separation distances required to install an antenna on a vehicle must be larger than those tested for compliance and must be disclosed separately to antenna installers and radio operators to ensure compliance. Please identify exactly what this means. Furthermore, please indicate if the disclosure requirements are something new, different and/or additional to what has been previously included in installation and operator manuals. Section IV(4) requires MPE evaluation procedures consistent with KDB 447498. What exactly does this require? Are MPE and/or SAR evaluation procedures allowed/required? How exactly is the ≤ 10 cm distance determined? (a diagram would be helpful.) Section IV(4ii) states Bystander exposure should be evaluated at a distance ≥ 20 from the edge of the vehicle, at the required locations, and must be ≤ 90 cm from the antenna. The test separation distance from the antenna must be in multiples of 15 cm or 6. What is the basis for the 20 cm, 90 cm and 15 cm or 6 distances? Section IV(6) states When more than 60 cm separation is required between the antenna and bystanders outside of the vehicle to maintain compliance, a caution label is required to alert the radio operator about his or her obligations to maintain bystander RF exposure requirements. o (i) This must be implemented as a permanent label on the microphone or at the end of the cord next to the microphone; for example, Caution: Persons outside of the vehicle must be kept x cm, or x.x ft, away from the antenna to comply with FCC RF exposure requirements during radio transmission. o (ii) The required bystander separation distance should be rounded up to the next 15 cm or 6 inches to facilitate applying the instruction Regarding the required labeling, what is required in view of the fact multiple combinations of antennas and radio power outputs will be allowed proving differing separation distances? Please identify the basis for the additional 15 cm distance and identify how that works? For example if a required separation distance is determined to be 85 cm, does that mean the label should identify a distance of 90 cm (60 cm plus 2 times 15 cm) or 100 cm (85cm plus 15 cm)? Since the word Caution has specific legal meaning in accordance with international norms should it be used as proposed? Maybe the word Attention would be appropriate, particularly in view of the fact there will likely be no control on maintaining the correct label for each installation once the initial configuration, installation and label attachment is completed. Who owns the responsibility for the Class II changes identified in Section IV (B2) states when differing manufacturers of the simultaneous transmitting equipment are involved? Section IV (B4) states All prohibited configurations must also be clearly identified in the antenna installation requirements and radio operator instructions. This is potentially a never ending list that is unknown to any reasonable person. We suggest the installation and operator manuals clearly identify the allowed combinations and specifically state that installation or operation of any other configurations is not allowed. The phrase may be acceptable is used in the introductory part of Section IV(C). Please identify the specific circumstances when utilization of FDTD simulations will be appropriate, or is a KBD inquiry for permission required in all cases? Given the potential impact of the proposed KDBs on test time, lab capacity, and even product design, we request that OET determine and announce a reasonable transition period for implementation of the KDBs once finalized. TIA members recommend that a transition period of at least ninety days in order to mitigate the impact that such extensive changes to testing protocols will have. TIA has previously requested an extension of the due date for comments on draft KDBs as critical to industrys ability to provide thoughtful comments. In order to facilitate review of industrys concerns, TIA may submit comments to selected KDBs, subject to supplementation, after June 30, 2012. We therefore respectfully submit this comment to draft KDB 643646, and urge the Commission to act consistent with the above. View attachment associated with this comment

Note: It is important to understand that the staff guidance provided in the KDB is intended to assist the public in following Commission requirements and does not constitute rules. Accordingly, the guidance is not binding on the Commission and will not prevent the Commission from making a different decision in any matter that comes to its attention for resolution.

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